First report of Colletotrichum siamense and Colletotrichum endophyticum associated with anthracnose on avocado (Persea americana Mill.) in Vietnam

The avocado anthracnose disease is mostly caused by Colletotrichum species, which accounts for the understandable decline in avocado production. This study is conducted to reveal Colletotrichum species causing avocado anthracnose using combined morphological characterization and multi-locus phylogenetic analysis based on the data sets of ITS region, ACT, CAL, CHS-1, GAPDH and TUB2 genes. Four isolates were obtained from avocados have anthracnose symptoms and identified as two species, including Colletotrichum siamense and Colletotrichum endophyticum. These Colletotrichum species were classified into the same group as the C. gloeosporioides species complex, which was the predominant pathogen involved in the anthracnose of avocados worldwide. This is the first detection of these two Colletotrichum species as the cause of anthracnose on avocados in Vietnam. The artificial inoculation using the wounded method demonstrated that four representative isolates were able to infect not only avocado but also mango and banana with different levels of aggressiveness. Most isolates exhibited higher pathogenicity on their original host than other hosts. C. endophyticum AD24.3 was the most virulent pathogen among the tested isolates, with the highest disease incidence and lesion diameters on three investigated fruit types. Our findings provide a preliminary understanding of Colletotrichum species associated with avocado anthracnose, which will be useful in developing biocontrol methods and the management of avocado post-harvest disease in Vietnam.